Lubricant Compositions Containing Stable Boric Acid Suspension

ABSTRACT

A lubricant composition including a lubricant comprising at least one of a hydrocarbon oil or grease, a surfactant, an ester of adipic acid, and a suspension of boric acid.

BACKGROUND OF THE INVENTION

This invention relates to a lubricant composition comprising a boric acid suspension.

Lubricity is an essential element for lengthening the usefulness of various motor and mechanical components which rely on lubricants such as petroleum-based greases and oils, synthetic oils, mineral oils, silicon oils, cutting oils, transmission fluids, hydraulic fluids, and the like.

Boric acid is environmentally safe, inexpensive, and has an unusual capacity to enhance the antifriction and antiwear properties of sliding metal surfaces. Boric acid is a crystalline compound, insoluble in hydrocarbons such as greases and oils.

There remains a great need for lubricants that provide high lubricity and low wear. There is a further need for stable suspensions that contain high concentrations of particulate boric acid in the lubricants and that have long shelf-lives. The present invention meets these needs and provides related advantages as well.

SUMMARY OF THE INVENTION

According to an aspect of the present invention a lubricant composition is provided comprising a lubricant comprising at least one of a hydrocarbon oil or grease; a surfactant; an ester of adipic acid linked to the lubricant; and a suspension of boric acid.

According to another aspect of the invention, a lubricant composition is provided comprising a lubricant comprising at least one of a hydrocarbon oil or grease and a boric acid reaction product comprising particulate boric acid and an ester of adipic acid linked to the lubricant.

It is an object of the present invention to provide a lubricant composition having superior lubricity thereby reducing wear on treated mechanical parts.

It is another object of the present invention to provide a lubricant composition having a high concentration of boric acid remaining suspended in both a concentrate and a finished lubricant composition.

It is an advantage of the present invention that the lubricant composition provides a shelf-life of up to about five years.

As used herein “substantially”, “generally”, “relatively”, and “about” are relative modifiers intended to indicate permissible variation from the characteristic so modified. It is not intended to be limited to the absolute value or characteristic which it modifies but rather approaching or approximating such a physical or functional characteristic.

DETAILED DESCRIPTION OF INVENTION

According to the present invention, a lubricant composition comprises a boric acid suspension.

In this detailed description, references to “one embodiment”, “an embodiment”, or “in embodiments” mean that the feature being referred to is included in at least one embodiment of the invention. Moreover, separate references to “one embodiment”, “an embodiment”, or “in embodiments” do not necessarily refer to the same embodiment; however, neither are such embodiments mutually exclusive, unless so stated, and except as will be readily apparent to those skilled in the art. Thus, the invention can include any variety of combinations and/or integrations of the embodiments described herein.

The lubricant composition comprises a lubricant comprising at least one of a hydrocarbon-based oil or grease. Examples of such an oil or grease include, but are not limited to, cutting oils, synthetic oils, mineral oils, silicon oils, engine oils, hydraulic fluids, mineral oils, vegetable oils, transmission fluids, e.g., oils for automatic transmissions, dry film lubricants, grease for bearings and jet turbines, mixtures thereof, and other lubricants that are non-reactive to boric acid. In specific embodiments, the lubricant may comprise a light petroleum base oil. Examples include, but are not limited to, ExxonMobil EHC-45 and Flint Hills Resources® 100-HC or 100-SN. In specific embodiments, the lubricant composition may comprise about 30 wt. % to about 60 wt. % of lubricant, based on the total weight of the lubricant composition.

According to the present invention, the lubricant composition comprises a monomer or prepolymer. The monomer or prepolymer may comprise adipic acid or a derivative thereof, such as an ester of adipic acid (an adipate). In specific embodiments, the monomer or prepolymer comprises diisodecyl adipate (DIDA), commercially available as Hatcol 2910 or Jayflex® DIDA (e.g., CAS 27178-16-1).

The monomer or prepolymer chemically links onto the lubricant via hydrogen-carbon bonds. Chemically linking polymer chains to the lubricant is effective because the polymer chains may double as surfactants. Polar sites on the polymer chains form bridges between boric acid and the lubricant, thus stabilizing the interaction between the two. In specific embodiments, the monomer or prepolymer may be dissolved in a solvent before adding to the lubricant.

According to the present invention, the lubricant composition comprises a surfactant. Suitable surfactants include, but are not limited to, dispersants such as Dow Triton™ X-100 (octylphenol ethoxylate), Uniquema Atlas™ G-5000 (polyalkylene glycol ether), and Lubrizol Ircosperse® 2174. Sufficient surfactant is used so that when particulate boric acid is added to the lubricant, the macro globule particles of the boric acid are broken up and prevented from reforming. In specific embodiments the lubricant composition comprises from 0.001 to about 0.5 wt. % (about 100 ppm to about 5000 ppm) surfactant, for example from about 0.025 to about 0.045 wt. % (about 250 ppm to about 450 ppm) surfactant, based on the weight of the lubricant composition.

According to the present invention, the lubricant composition comprises particulate boric acid. In specific embodiments, the boric acid is advantageously produced by the low temperature jet-milling of commercially available boric acid. The conditions of the low temperature jet-milling process can be adjusted to produce boric acid particles having an average particle size of 65 microns or less, as desired. In specific embodiments, the boric acid has a particle size in the range of from about 0.1 to about 2.5 microns, for example in the range of from about 0.5 to about 1 micron.

A boric acid reaction product is formed with a chemically-linked lubricant. Without wishing to be bound by a theory, it is believed that the boric acid's hydroxyl groups may become loosely associated with lubricant. When the monomer or prepolymer is chemically linked onto the lubricant, the resulting polymer chains effectively stabilize the boric acid-lubricant association and create a stable reaction product, effectively suspending the boric acid particles in the lubricant.

According to the present invention, the lubricant composition may be made by mixing boric acid, surfactant, monomer/prepolymer, and lubricant to obtain a concentrate containing the boric acid reaction product or suspension. In specific embodiments, the components may be high shear blended, for example, for about 15 minutes at about 5000 rpm, and at ambient pressure, not to exceed 120° F. In specific embodiments, a graft initiator and/or catalyst is not used in the process of making the concentrate or final lubricant composition.

In specific embodiments, the concentrate comprises about 5 to about 25 wt. % (about 50,000 ppm to about 250,000 ppm) particulate boric acid, based on the total weight of the concentrate, suspended in the lubricant.

In specific embodiments, the concentration of the ester of adipic acid in the concentrate solution may vary within practically any limits, for example, from between about 0.1 to about 50 wt. % (about 1,000 ppm to 500,000 ppm), for example, between about 1 to about 20 wt. % (about 10,000 ppm and about 200,000 ppm), based on the weight of the concentrate.

The concentrate may be diluted with additional lubricant to form a final lubricant composition comprising from about 0.001 to about 20 wt. % (about 10 ppm to about 200,000 ppm) boric acid, for example about 0.003 to about 0.5 wt. % (about 30 ppm to about 5,000 ppm) boric acid, based on the total weight of the finished lubricant composition. The concentration of surfactant in the finished lubricant composition may be from about 0.0002 to about 0.0006 wt. % (about 2 ppm to about 6 ppm). The concentration of adipic acid ester in the finished lubricant composition may be from about 5 wt. % to about 50 wt. % (about 50,000 to about 500,000 ppm).

Both the concentrate and the finished lubricant composition remain stable, even when subjected to a variety of potentially destabilizing conditions. For example, the boric acid remains suspended at temperatures ranging from about to about −30° F. to 150° F. and is shelf stable for up to about five years. Moreover, the finished lubricant compositions provide superior lubricity and reduced wear on mechanical components of the internal combustion engine, while preventing corrosion.

The following are non-limiting examples of embodiments of the present invention.

EXAMPLE 1

Five thousand, 5000, parts Dow Triton X-100 surfactant are added to 500,000 parts Hatco 2910 diisodecyl adipate in a reaction vessel and 200,000 parts boric acid are slowly added to the reaction vessel and a homogeneous slurry is formed. 395,000 parts lubricant ExxonMobil EHC-45 oil is slowly added to the slurry and is stirred for thirty minutes in a high shear blender.

EXAMPLE 2

COMPONENT Wt. % (ppm) Diisodecyl 40 (400,000) Adipate (DIDA) Boric Acid (1 um) 20 (200,000) High Shear, do not exceed 120° F. Dow Triton X-100 .5 (5,000)   High Shear 15 minutes, do not exceed 120° F. Add lubricant (10%/minute) 100-SN or EHC-45 39.5 (395,000)   Lubricant High Shear 30 minutes, do not exceed 120° F. When complete, cool to Room Temperature Store in Airtight Container

While various aspects of the present invention have been particularly shown and described with reference to the exemplary, non-limiting, embodiments above, it will be understood by those skilled in the art that various additional aspects and embodiments may be contemplated without departing from the spirit and scope of the present invention.

Other aspects, objects and advantages of the present invention can be obtained from a study of the drawings, the disclosure and the appended claims. 

1. A lubricant composition, comprising: a lubricant comprising at least one of a hydrocarbon oil or grease; about 0.001 wt.% to about 0.5 wt .% of a surfactant comprising octylphenol ethoxylate or polyalkylene plycol ether; an ester of adipic acid chemically-linked to the at least one lubricant; and a suspension of particulate boric acid, wherein the boric acid has a particle size of 0.5 to 2.5 microns.
 2. A lubricant composition according to claim 1, wherein the ester of adipic acid comprises diisodecyl adipate.
 3. A lubricant composition according to claim 1, wherein the lubricant comprises at least one of a synthetic oil, a mineral oil, a silicon oil, a cutting oil, a transmission fluid, a hydraulic fluid, or a grease.
 4. (canceled)
 5. A lubricant composition according to claim 1, wherein the boric acid has a particle size of 0.5 to about 1 micron.
 6. (canceled)
 7. A lubricant composition according to claim 1, comprising 5 wt.% to about 25 wt.% boric acid based on the weight of the lubricant composition. 8-10. (canceled)
 11. A lubricant composition, comprising: a lubricant comprising at least one of a hydrocarbon oil or grease; about 0.001 wt.% to about 0.5 wt.% of a surfactant comprising polyalkylene glycol ether; and a boric acid suspension comprising particulate boric acid and diisodecyl adipate chemically linked to the lubricant, wherein the boric acid has a particle size of 0.5 to 2.5 microns.
 12. (canceled)
 13. A method of making a lubricant composition comprising a stable boric acid suspension, said method comprising: mixing an ester of adipic acid, a surfactant comprising octylphenol ethoxylate or polyalkylene glycol ether, and boric acid having a particle size of 0.5 to 2.5 microns to form a mixture by high shear blending, wherein a temperature of the mixture does not exceed 120° F.; adding a lubricant comprising at least one of a hydrocarbon oil or grease to the mixture; chemically linking the ester of adipic acid to the at least one lubricant and forming a suspension of boric acid in the at least one lubricant.
 14. A method according to claim 13, further comprising dissolving an ester of adipic acid comprising diisodecyl adipate in a solvent. 15-16. (canceled)
 17. A method according to claim 13, wherein a graft initiator and catalyst are not used in making the lubricant composition.
 18. A lubricant composition according to claim 1, wherein the ester of adipic acid comprises a monomer or prepolymer that is chemically linked to the at least one lubricant via polymer chains.
 19. A lubricant composition according to claim 18, wherein polar sites on the polymer chains form bridges between the particulate boric acid and the at least one lubricant.
 20. A lubricant composition according to claim 1, wherein the ester of adipic acid is chemically-linked to the at least one lubricant via hydrogen-carbon bonds.
 21. A lubricant composition according to claim 1, wherein the surfactant comprises octylphenol ethoxylate.
 22. A lubricant composition according to claim 1, comprising about 200,000 ppm of boric acid.
 23. A lubricant composition according to claim 1, wherein the surfactant comprises polyalkylene glycol ether.
 24. A lubricant composition according to claim 1, comprising: 30 wt.% to 60 wt.% of at least one lubricant comprising a hydrocarbon oil or grease, based on the total weight of the lubricant composition; 5 wt.% to 50 wt.% of diisodecyl adipate chemically-linked to the at least one lubricant; and 5 wt.% to 25 wt.% of particulate boric acid, suspended in the at least one lubricant.
 25. A lubricant composition according to claim 1, comprising 20 wt.% to about 25 wt.% of particulate boric acid, suspended in the at least one lubricant.
 26. A lubricant composition according to claim 1, wherein the lubricant comprises a silicon oil.
 27. A lubricant composition according to claim 1, wherein the lubricant comprises a hydraulic fluid. 